Magnetic sensor used for lf communication in tpms application

ABSTRACT

A tire pressure monitoring system (TPMS) sensor and a communication method are provided. The TPMS sensor includes a microcontroller unit, a pressure sensor electrically connected to the microcontroller unit and configured to measure an internal air pressure of a tire and a receiver electrically connected to the microcontroller unit and configured to receive at least one communication signal. The receiver includes a magnetic sensor configured to detect a modulated low-frequency electromagnetic carrier signal as a first communication signal and output an encoded measurement signal based on the detected modulated low-frequency electromagnetic carrier signal. The TPMS sensor further includes a demodulator configured to convert the encoded measurement signal into a data signal and output the data signal to the microcontroller unit.

FIELD

The present disclosure relates generally to a tire pressure monitoringsystem, and, more particularly, to a tire pressure sensor having amagnetic sensor for receiving low frequency communications.

BACKGROUND

Tire Pressure Monitoring Systems (TPMS) play an important role invehicle safety and emissions reduction. Several countries and governingbodies have enacted mandatory regulations that require vehicles to haveTPMS; for example U.S., European Union & Korea. A majority of thismarket is served by direct tire pressure monitoring systems, in whicheach tire contains a TPMS sensor module. Due to this high marketpenetration, the cost and the size of these sensor modules is of highimportance. Current sensor modules consist of a tire pressure sensor(TPS) integrated circuit, a battery, antennas for communication, and avery small number of discrete passive electrical components.

Most sensor modules use a motion detection sensor to conserve the lifeof the sensor module's battery by entering power-down mode while thevehicle is parked. In this way, the service life of the sensor and itsnon-replaceable battery can be maximized. The typical motion detectionsensor responds to g-force and is either an accelerometer or a shocksensor.

One requirement of the sensor module is to that of a bi-directionalcommunication link. The uplink communication channel from the sensormodule towards the TPMS receiver of an electronic control unit (ECU) istypically over an ultra-high frequency (UHF) radio link. The downlinkcommunication channel towards the sensor is mainly used in during theproduction and testing of the sensor prior to installation in a tire andwheel assembly. TPMS sensors are able to receive data on the downlinkfrom a low frequency (LF, typically 125 kHz) transmitter. Therefore, thetypical TPS integrated circuit (IC) includes an LF receiver circuit. TheLF receiver circuitry within the IC is connected to a resonant LFantenna network. This network typically consists of a capacitor, aresistor and a wire wound high sensitivity coil. The LF antennacircuitry is all contained within the confines of the sensor module.

The LF antenna coil is constrained by physics. It consists of a highpermeability (μ_(r)) core, with many turns of fine-gage wire wrappedaround it. The wire ends are terminated and the entire assembly iscontained within a form that is compatible with printed circuit board(PCB) assembly equipment. The coil is delicate, costly, and somewhatimmune to the size reduction that occurs with other passive electroniccomponents. A typical LF antenna network costs about 0.15

and occupies around 20 mm² of PCB area. The possibility to furthershrink the LF antenna is limited by physics. A smaller size antennarequires a higher sensitivity receiver. This, in turn, requires moreoperating current. Unless a higher communication frequency is chosen,the LF coil will likely remain the same size for the foreseeable future.

Furthermore, the LF antenna is resonant, in order to provide a voltageamplification of the very small (on the order of millivolts) voltageinduced across the LF antenna coil. The resonant antenna networktypically has a Q factor on the order of 5-10. One disadvantage of aresonant antenna is that magnetic impulse energy, e.g., from solenoids,relays or motors, will excite the resonant antenna and cause it to“ring” at its resonant frequency. These impulse noise events occur oftenin vehicles, and can disrupt LF communication from taking place.

There is a second type of uplink that has been used in the past withTPMS, that of a magnetic reed switch that, when actuated, initiates a“learn mode” in the TPMS sensor. Historically, this has been implementedusing a mechanical switch. The advantage of this sort of uplink is thatthe only tool required is a permanent magnet. However, the magnetic reedswitch has proven to be a reliability risk in terms of surviving theharsh mechanical environment that a TPMS sensor must endure.Furthermore, the size of the switch is significant (e.g., typicallyabout 12 mm in length and about 2 mm in diameter). Like the LF antennacoil, the magnetic reed switch will likely remain the same size for theforeseeable future.

Therefore, an improved device that retains the LF uplink functionalityrequired by the TPMS sensor module without incurring additional bulk andcost may be desirable.

SUMMARY

Embodiments further provide a device having a tire pressure monitoringsystem (TPMS) sensor and a communication method are provided.

According to one or more embodiments, a TPMS sensor includes amicrocontroller unit, a pressure sensor electrically connected to themicrocontroller unit and configured to measure an internal air pressureof a tire and a receiver electrically connected to the microcontrollerunit and configured to receive at least one communication signal. Thereceiver includes a magnetic sensor configured to detect a modulatedlow-frequency electromagnetic carrier signal as a first communicationsignal and output an encoded measurement signal based on the detectedmodulated low-frequency electromagnetic carrier signal. The TPMS sensorfurther includes a demodulator configured to convert the encodedmeasurement signal into a data signal and output the data signal to themicrocontroller unit.

According to one or more embodiments, a method for communicating with atire pressure monitoring system (TPMS) sensor that includes amicrocontroller unit and a receiver is provided. The receiver iselectrically connected to the microcontroller unit and is configured toreceive at least one communication signal using a magnetic sensor. Themethod includes detecting, by the magnetic sensor, a modulatedlow-frequency electromagnetic carrier signal as a first communicationsignal, outputting, by the magnetic sensor, an encoded measurementsignal based on the detected modulated low-frequency electromagneticcarrier signal, converting, by a demodulator, the encoded measurementsignal into a data signal, and outputting, by the demodulator, the datasignal to the microcontroller unit.

According to one or more embodiments, the method may further includedetecting, by the magnetic sensor, static magnetic fields, andtransmitting, by the magnetic sensor, magnetostatic field information tothe microcontroller unit.

According to one or more embodiments, the method may further includeselectively bypassing, by a bypass circuit, the demodulator such thatmicrocontroller unit receives the magnetostatic field information fromthe magnetic sensor, instead of a signal from the demodulator, when thebypass circuit is enabled.

According to one or more embodiments, the method may further includereceiving, by the receiver, an antenna signal generated from a secondcommunication signal received by an external antenna coil, andselectively outputting, by a multiplexer, one of a first signal or asecond signal to the microcontroller unit, wherein the first signal isderived from the magnetic sensor and the second signal is derived fromthe antenna signal. The first signal may correspond to a signal based ondetecting the modulated low-frequency electromagnetic carrier signal orthe static magnetic fields.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described herein making reference to the appendeddrawings.

FIG. 1 illustrates a TPMS sensor including a magnetic sensor accordingto one or more embodiments;

FIG. 2 illustrates a time-domain plot of a modulated carrier signalimplemented according to one or more embodiments;

FIG. 3 illustrates a time-domain plot of another modulated carriersignal implemented according to one or more embodiments;

FIG. 4 illustrates a block diagram of a LF receiver and demodulationcircuit according to one or more embodiments;

FIG. 5 illustrates a block diagram of another LF receiver anddemodulation circuit according to one or more embodiments; and

FIG. 6 illustrates a block diagram of another LF receiver anddemodulation circuit according to one or more embodiments.

DETAILED DESCRIPTION

In the following, various embodiments will be described in detailreferring to the attached drawings. It should be noted that theseembodiments serve illustrative purposes only and are not to be construedas limiting. For example, while embodiments may be described ascomprising a plurality of features or elements, this is not to beconstrued as indicating that all these features or elements are neededfor implementing embodiments. Instead, in other embodiments, some of thefeatures or elements may be omitted, or may be replaced by alternativefeatures or elements. Additionally, further features or elements inaddition to the ones explicitly shown and described may be provided, forexample, conventional components of sensor devices. Furthermore,well-known structures and devices are shown in block diagram form ratheror in a schematic view rather than in detail in order to avoid obscuringthe embodiments.

Features from different embodiments may be combined to form furtherembodiments, unless specifically noted otherwise. Variations ormodifications described with respect to one of the embodiments may alsobe applicable to other embodiments.

Connections or couplings between elements shown in the drawings ordescribed herein may be wire-based connections or wireless connectionsunless noted otherwise. Furthermore, such connections or couplings maybe direct connections or couplings without additional interveningelements or indirect connections or couplings with one or moreadditional intervening elements, as long as the general purpose of theconnection or coupling, for example to transmit a certain kind of signalor to transmit a certain kind of information, is essentially maintained.

Embodiments relate to sensors and sensor systems and to obtaininginformation about sensors and sensor systems. A sensor may refer to acomponent which converts a physical quantity to be measured to anelectric signal, for example, a current signal or a voltage signal. Thephysical quantity may for example comprise a magnetic field, an electricfield, a pressure, a force, a current or a voltage, but is not limitedthereto.

A sensor device as used herein may refer to a device which comprises asensor and further components, for example biasing circuitry, ananalog-to-digital converter or a filter. A sensor device may beintegrated on a single chip, although in other embodiments a pluralityof chips or also components external to a chip may be used forimplementing a sensor device.

A sensor module is provided that includes a magnetic field sensor thatis integrated into a TPMS sensor integrated circuit. In particular, themagnetic field sensor replaces the PCB-mounted LF antenna coil andassociated components for the TPMS LF uplink function. The magneticfield sensor is integrated into the TPMS sensor integrated circuit,either as a separate die inside the integrated circuit package, ormonolithically as a part of the TPMS sensor die itself, and isconfigured to detect a LF communication field (i.e., a communicationsignal).

Magnetic field sensors are active detectors/receivers used in manyapplications to sense a magnetic field and variations thereof. In one ormore embodiments, a magnetic field sensor may be a magneto-resistivesensor. Magneto-resistive sensors are often referred to as xMR sensors,which is a collective term for anisotropic magneto-resistive (AMR),giant magneto-resistive (GMR), and tunneling magneto-resistive (TMR).The sensor package may also include a signal processing circuit thatreceives a sensor signal (e.g., raw measurement data from the magneticfield sensor element) and derives, from the sensor signal, a measurementsignal that represents the sensed magnetic field.

In particular, a TMR sensor may be used as the magnetic field sensor ofthe disclosed embodiments, although the embodiments are not limitedthereto. TMR offers an advantage that it can detect both time-varyingand static magnetic fields. Therefore, a single TMR sensing element maybe able to provide both LF uplink and magnetostatic LF uplinkfunctionality. This would be particularly advantageous, for example, ina sensor that is intended to emulate existing sensors (e.g., the LFuplink and magnetic switch uplink functions may be provided with noadditional cost or size penalties). Further, it will be appreciated thatthe terms “sensor” and “sensing element” may be used interchangeablythroughout this description.

FIG. 1 illustrates a monolithic TPMS sensor 100 including a receiver 10that includes a magnetic sensor 11 according to one or more embodiments.The TPMS sensor 100 is a direct TPMS sensor mounted inside the tire. Amagnetic sensor 11 can be incorporated as part of a typicalsemiconductor technology. Therefore, a magnetic sensor 11 can enable amonolithic TPMS sensor 100 which includes the TMR sensor 11, amicrocontroller unit (MCU) 12, radio frequency (RF) transmitter 13, anda microelectromechanical systems (MEMS) pressure sensor 14. A powersupply 15 (e.g., a battery cell) is further provided to supply power tothe TPMS sensor 100 and its components. Thus, disadvantages of multipledies are not incurred, nor are LF antenna coils or magnetic reedswitches required.

In particular, the magnetic sensor 11 is configured to receive LFcommunication signals from a vehicle electronic control unit (ECU), asetting tool, a diagnostic and testing tool, and the like. The MCU 12,is configured to receive signals from one or more components of the TPMSsensor 100, process the received signals and control the components viacontrol signals. The MCU 12 may further include one or more memorydevices or be electrically connected to one or more memory devicesprovided in the TPMS sensor 100. The RF transmitter 13 is electricallyconnected to the MCU 12 and is configured to transmit a radio signal tothe vehicle ECU, the setting tool, or the diagnostic and testing tool.The RF transmitter 13 may transmit a signal (e.g., data and/or feedbackinformation) to the vehicle ECU, the setting tool, or the diagnostic andtesting tool in response to the magnetic sensor 11 receiving an LFsignal (e.g., data in the form of information or a command) from thevehicle ECU, the setting tool, or the diagnostic and testing tool. Thepressure sensor 14 is electrically connected to the MCU 12 andconfigured to measure the internal air pressure of a tire.

While not shown in FIG. 1, the TPMS sensor 100 may further include atemperature sensor electrically connected to the MCU 12 and configuredto measure the internal temperature of the tire, and an accelerationsensor electrically connected to the MCU 12 and configured to measurethe acceleration of the tire.

While the TPMS sensor 100 is illustrated as a monolithic device (i.e.,single die integration), it will be understood that one or morecomponents (e.g., the magnetic sensor 11) may be provided on a separatedie inside the integrated circuit package of the TPMS sensor 100.

As mentioned above, the magnetic sensor 11 may be a TMR sensor, but isnot limited thereto. In general, the magnetic sensor 11 is configured asa receive-only antenna to sense a magnetic field, convert the sensedmagnetic field into a corresponding signal, and to output a signal tothe MCU 12 or to other signal processing circuitry. In particular, themagnetic sensor 11 is configured to receive communication signals overan electromagnetic field by a modulated low-frequency electromagneticcarrier signal (i.e., carrier signal) that is modulated, for example, byamplitude shift keying (ASK). The carrier signal has a carrier frequency(e.g., low-frequency) such that, when the carrier signal is present, theelectromagnetic field oscillates between a north-pole polarity and asouth-pole polarity at the carrier frequency which produces analternating magnetic field detected by the magnetic sensor 11. Afrequency band below 300 kHz is “low frequency”, and, more particularly,between 30 kHz and 300 kHz. In this way, the carrier signal can bemodulated as a command code representing a specific command that can bereceived by the magnetic sensor 11 and decoded by signal processingcircuitry to provide a command to the MCU 12. Additionally, the carriersignal may by encoded to provide data to the TPMS sensor 100.

ASK is a form of amplitude modulation that represents digital data asvariations in the amplitude of a carrier signal. In one embodiment of anASK system, the binary symbol 1 is represented by transmitting afixed-amplitude carrier signal and fixed frequency for a bit duration ofT seconds. If the signal value is 1 then the carrier signal will betransmitted; otherwise, a signal value of 0 will be transmitted. Thespecific time pattern of on/off times of the carrier signal, includingthe duration thereof, represents the modulation of the carrier signaland, hence, the encoding of the information in the signal. ASK uses afinite number of amplitudes, and usually, each amplitude encodes anequal number of bits. A demodulator, which is designed specifically forthe symbol-set used by the modulator, determines the amplitude of thereceived signal and maps it back to the symbol it represents, thusrecovering the original data. The frequency of the carrier signal iskept constant.

The magnetic sensor 11 may be a single axis or a multiple axis magneticsensor, and, in particular, may be an earth magnetic field sensor. Thatis, the magnetic sensor 11 is configured with a high sensitivity,sensitive enough to detect a small magnetic field having a magnitude ina range of the Earth's magnetic field (e.g., 25 to 65 microteslas).Thus, an earth magnetic field sensor can sense variations in the Earth'smagnetic field. In other embodiments, the magnetic sensor 11 may besingle axis or multiple axis magnetic sensor that is sensitive enough todetect a magnetic field with a magnitude in the order of nano-Teslas(nT, e.g., in the range of 1 to 10 nT).

Furthermore, the magnetic sensor 11 should be fast enough to detect andrespond to a modulated low-frequency carrier signal in order to outputthe coded information, either in the form of an analog or a digitalsignal. For example, the magnetic sensor 11 may include one or moresensor elements and an analog-to-digital converter (ADC) that convertsthe analog signal from the one or more sensor elements to a digitalsignal. The magnetic sensor 11 may also include a digital signalprocessor (DSP) that performs some processing on the digital signal, tobe discussed below.

Thus, the magnetic sensor 11 may be a TMR sensor. TMR sensors haveenough sensitivity to detect earth's magnetic field range (+/−1000 mG).TMR sensors also exhibit low current consumption because the currentwhich passes into TMR layer is very small due to its use of thetunneling effect. For example, a 3-axis earth magnetic field sensorbased on TMR principle may be used as the magnetic sensor 11.

As described above, the TPMS sensor 100 may be completely monolithic andthe magnetic sensor 11 is configured to receive communications over anelectromagnetic field by a modulated low-frequency electromagneticcarrier signal (i.e., carrier signal) that is modulated, for example, byASK. The carrier signal has a carrier frequency (e.g., low-frequency)such that, when the carrier signal is present, the electromagnetic fieldoscillates between a north-pole polarity and a south-pole polarity atthe carrier frequency which produces an alternating magnetic fielddetected by the magnetic sensor 11. Thus, the modulated low-frequencycarrier signal is encoded with a time pattern that representsinformation (e.g., a command, information or other data) transmitted onthe downlink channel to the TPMS sensor 100 and detected by the magneticsensor 11. A magnetic sensor signal is then output from the magneticsensor 11 such that the encoding of the carrier signal, and thus thetransmitted information, can be determined by the TPMS sensor 100 (e.g.,by the MCU 12).

The MCU 12 may receive raw measurement data (e.g., analog signals)output from the magnetic sensing element of the magnetic sensor 11 basedon the modulated carrier signal. The MCU 12 may include a LF receiverand demodulation circuit to process the raw measurement data and decodethe information conveyed by the raw measurement data. Upon decoding theinformation, the MCU 12 may perform a function in response to thedecoded information. For example, the MCU 12 may command the RFtransmitter 13 via a control signal to transmit feedback information(e.g., tire pressure information, sensor ID, status information, or thelike). Alternatively, some or all of LF receiver and demodulationcircuitry may be provided in the TPMS sensor 100 external to the MCU 12,which ultimately receives the decoded information. For example, themagnetic sensor 11 may include at least a portion of the LF receiver anddemodulation circuitry, perform processing on the raw measurement data,and output a digital signal to the MCU 12 for further processing of thedigital signal.

In view of the above, LF uplink magnetic field communication isprovided. For example, FIG. 2 illustrates an example of a time-domainplot of the 125 KHz modulated carrier signal (aliased) over time (t)that is transmitted as a LF uplink magnetic field communication and isdetected by the magnetic sensor 11. Specifically, FIG. 2 illustrates aslow ASK modulated 125 kHz carrier signal that uses a range of about0.5-2.0 seconds for the “on” time. For example, the carrier signal ismodulated such that the carrier signal is present or not present, thetime pattern of which represents the encoded information. As shown inFIG. 2, the carrier signal is present for 1.18 seconds, not present for0.78 seconds, and present again for 2.0 seconds. When the carrier signalis present, the magnetic field oscillates between its north and southpoles at the carrier frequency (e.g., 125 kHz). The magnetic sensor 11is configured to detect the presence of the carrier signal at thecarrier frequency or the absence thereof.

FIG. 3 illustrates another example of a 125 KHz modulated carrier signalthat is detected by the magnetic sensor 11. Specifically, FIG. 3illustrates a 3.96 kbps Manchester encoded ASK modulated 125 KHz carriersignal. Each “pulse” represents the presence of the carrier signaltransmitted at the carrier frequency. Manchester coding is a line codein which the encoding of each data bit is either low then high, or highthen low, of equal time. Thus, processing circuitry of the TPMS sensor100 is configured to receive a measurement signal from the magneticsensor 11 in order to decode the information. In particular, the carriersignal can be modulated to represent different parts of a datatransmission (e.g., a preamble, sync sequence, a wakeup ID, data, andthe like).

The LF uplink magnetic field communication described above can be usedsuch that the carrier signal is modulated with a command code or otherinformation. For example, during manufacturing of the TPMS sensor 100, atester may transmit a command to the TPMS sensor 100 (i.e., the magneticsensor 11) to verify that two-way communication is working properly. Ifthe tester receives a verification signal from the RF transmitter 13, itcan be assumed that the magnetic sensor 11 received the commandproperly.

In another example, the magnetic sensor 11 may be further configured toreceive a sensor ID number associated with the TPMS sensor 100 by asetting tool. Alternatively, the sensor ID may be programmed into theMCU 12 during manufacturing. However, once the sensor ID is stored in amemory of the TPMS sensor 100, the magnetic sensor 11 may receive acommand signal to transmit the sensor ID. For example, in response tothe command signal, the RF transmitter 13 may be configured by the MCU12 to transmit the sensor ID to an ECU upon installing the tire on thevehicle so that the sensor ID is coded into the vehicle.

In another example, the magnetic sensor 11 may receive a test signal(e.g., a trigger command or a status inquiry signal) to allow a testerto evaluate an operational state (e.g., working or not working) of theTPMS sensor 100 or to acquire information about the tire (e.g.,pressure, temperature, acceleration, etc.). In response to the magneticsensor 11 receiving the test signal, the RF transmitter 13 may beconfigured by the MCU 12 to transmit a response signal that indicatesthat the test signal was received by the TPMS sensor 100.

FIG. 4 illustrates a block diagram of a LF receiver and demodulationcircuit 400 according to one or more embodiments. The LF receiver anddemodulation circuit 400 is integrated in the TPMS sensor (e.g., theTPMS sensor 100 shown in FIG. 1). In particular, the LF receiver anddemodulation circuit 400 includes a magnetic sensor 411, amplifiers 412,an automatic gain control 413, an ASK demodulator 414, a data slicer andsampler 415, a low pass filter 416, a decoder 417, a receive buffer 418and a pattern matching unit 419.

The amplifiers 412 receive the input signal from the magnetic sensor 411and output an amplified input signal to the ASK demodulator 414. The ASKdemodulator 414 receives the amplified input signal from the amplifiers412 and is configured to recover the information content from themodulated carrier signal, detected by the magnetic sensor 411, andoutput a digital signal representing the information (e.g., a binarydata).

One or more of the components of the LF receiver and demodulationcircuit 400 may be incorporated into an MCU of the TPMS sensor,integrated separately on the die of the TPMS sensor, or a combinationthereof.

FIG. 5 illustrates a block diagram of a LF receiver and demodulationcircuit 500 according to one or more embodiments. In particular, the LFreceiver and demodulation circuit 500 incorporates dual functionality ofreceiving an input signal from one of a magnetic sensor and an externalLF antenna coil. Thus, the LF receiver and demodulation circuit 500 canbe selectively configured to receive and process an input signal fromthe magnetic sensor or the external LF antenna coil to be compatible forusers which implement different communication systems (e.g., magneticfield link communication or traditional LF link communication).

The LF receiver and demodulation circuit 500 includes a magnetic sensor511, amplifiers 512, an automatic gain control 513 and an ASKdemodulator 514, a data slicer and sampler 515, a low pass filter 516, adecoder 517, a receive buffer 518 and a pattern matching unit 519. Inaddition, the LF receiver and demodulation circuit 500 includes anattenuator 520 configured to receive an input signal from an external LFantenna coil (not shown), amplifiers 521, an automatic gain control 522,a detector 523, and a multiplexer 524.

The multiplexer 524 is configured to select, via receipt of an inputselect signal, a signal from the magnetic sensor branch or the LFantenna coil branch of the receiver circuit. The selected signal isoutput from the multiplexer 524 for further processing by the subsequentcomponents. Thus, a TPMS sensor that implements the LF receiver anddemodulation circuit 500 can be used in both communication systems.

One or more of the components of the LF receiver and demodulationcircuit 500 may be incorporated into an MCU of the TPMS sensor,integrated separately on the die of the TPMS sensor, or a combinationthereof.

In addition to LF uplink magnetic field communication, magnetostaticuplink communication may also be provided by the TPMS sensor (e.g., TPMSsensor 100). xMR sensors (e.g., GMR, AMR, TMR, etc.) are sensitive tomagnetic field orientation of the applied magnetic field. Thus, themagnetic sensor, such as a TMR sensor, may be configured to respond toboth time-varying as well as static magnetic fields. For example, themagnetic sensor 11 may be a single or multiple axis magnetic sensor,such as a TMR sensor, that is configured to detect the motion of vehicleby detecting static magnetic fields (e.g., Earth's magnetic fields), aswell as time-varying magnetic fields described above for enablingwireless communication.

In particular, the magnetic sensor 11 may be configured as anacceleration sensor (e.g., an accelerometer) to sense the Earth'smagnetic field to detect, for example, that a wheel is rotating. Forexample, changes in the sensor output may be detected as a wheel movesthrough the static magnetic fields of the Earth, and the detected changecan be used to calculate the acceleration. In addition or in thealternative, the magnetic sensor 11 may be configured as an magnetometer(e.g., a compass) to sense where the strongest magnetic force is comingfrom, which is generally used to detect magnetic north. Thus, underthese applications, the magnetic sensor 11 should be a type of sensor(e.g., TMR sensor) sensitive enough to sense variations in the magneticfield of the Earth. By implementing magnetic sensor 11 for LFcommunications and other sensor applications, additional technicalbenefits (e.g., lower current consumption, higher speed accuracy, etc.)may be realized which reduces overall system cost and increases systemperformance.

When a magnetic sensor type that is capable of responding to bothtime-varying as well as static magnetic fields is employed, e.g., a TMRtype, the signal processing is a bit different between modulated andunmodulated cases. Nevertheless, many common elements remain. Forexample, FIG. 6 illustrates a block diagram of a LF receiver anddemodulation circuit 600 according to one or more embodiments.

Similar to FIG. 5, the LF receiver and demodulation circuit 600 shown inFIG. 6, includes a magnetic sensor 611, amplifiers 612, an automaticgain control 613 and an ASK demodulator 614, a data slicer and sampler615, a low pass filter 616, a decoder 617, a receive buffer 618 and apattern matching unit 619. In addition, the LF receiver and demodulationcircuit 600 includes an attenuator 620 configured to receive an inputsignal from an external LF antenna coil (not shown), amplifiers 621, anautomatic gain control 622, a detector 623, and a multiplexer 624. Inaddition, a bypass circuit 625 is provided to enable the detection ofstatic magnetic fields. The bypass circuit 625 is enabled by ademodulation bypass signal. When enabled, the bypass circuit 625receives the input signal from the magnetic sensor 611 (via theamplifiers 612) and provides the input signal to the multiplexer 624.Thus, the ASK demodulator 614 is bypassed and the multiplexer 624receives a signal from the bypass circuit 625 instead of from the ASKdemodulator 614. The signal is then output by the multiplexer 624 andprocessed by the rest of the LF receiver and demodulation circuit 600.Accordingly, the LF receiver and demodulation circuit 600 provides theability to support an internal integrated magnetic field detector (e.g.,a TMR sensing element) and external LF antenna coil for modulated LFuplink communications, as well as the possibility to support anunmodulated magnetostatic uplink communications.

One or more of the components of the LF receiver and demodulationcircuit 600 may be incorporated into an MCU of the TPMS sensor,integrated separately on the die of the TPMS sensor, or a combinationthereof.

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus. Some or all of the method steps may be executed by (or using)a hardware apparatus, like for example, a microprocessor, a programmablecomputer or an electronic circuit. In some embodiments, some one or moreof the method steps may be executed by such an apparatus.

Depending on certain implementation requirements, embodiments providedherein can be implemented in hardware or in software. The implementationcan be performed using a digital storage medium, for example a floppydisk, a DVD, a Blue-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or aFLASH memory, having electronically readable control signals storedthereon, which cooperate (or are capable of cooperating) with aprogrammable computer system such that the respective method isperformed. Therefore, the digital storage medium may be computerreadable.

The above described exemplary embodiments are merely illustrative. It isunderstood that modifications and variations of the arrangements and thedetails described herein will be apparent to others skilled in the art.It is the intent, therefore, to be limited only by the scope of theimpending patent claims and not by the specific details presented by wayof description and explanation of the embodiments herein.

What is claimed is:
 1. A tire pressure monitoring system (TPMS) sensorcomprising: a microcontroller unit; a pressure sensor electricallyconnected to the microcontroller unit and configured to measure aninternal air pressure of a tire; a receiver electrically connected tothe microcontroller unit and configured to receive at least onecommunication signal, the receiver including a magnetic sensorconfigured to detect a modulated low-frequency electromagnetic carriersignal as a first communication signal and output an encoded measurementsignal based on the detected modulated low-frequency electromagneticcarrier signal; and a demodulator configured to convert the encodedmeasurement signal into a data signal and output the data signal to themicrocontroller unit.
 2. The TPMS sensor of claim 1, wherein the TPMSsensor is monolithic.
 3. The TPMS sensor of claim 1, wherein themodulated low-frequency electromagnetic carrier signal is an amplitudeshift keying (ASK) modulated low-frequency electromagnetic carriersignal.
 4. The TPMS sensor of claim 1, wherein the magnetic sensor is anearth magnetic field sensor having a sensitivity to sense at least amagnitude equivalent to a magnitude of an Earth magnetic field.
 5. TheTPMS sensor of claim 1, wherein the magnetic sensor is an multiple axismagnetic sensor.
 6. The TPMS sensor of claim 1, wherein the magneticsensor is a tunneling magneto-resistive (TMR) sensor.
 7. The TPMS sensorof claim 1, wherein the magnetic sensor is configured to detecttime-varying magnetic fields for receiving the modulated low-frequencyelectromagnetic carrier signal and static magnetic fields for providingmagnetostatic field information to the microcontroller unit.
 8. The TPMSsensor of claim 7, wherein the microcontroller unit is configured todetect changes in a sensor output of the magnetic sensor as the magneticsensor passes through the static magnetic fields and calculate anacceleration of the tire based on the detected changes in the sensoroutput.
 9. The TPMS sensor of claim 7, wherein the microcontroller unitis configured to calculate compass information based on themagnetostatic field information.
 10. The TPMS sensor of claim 7, furthercomprising a bypass circuit configured to selectively bypass thedemodulator such that microcontroller unit receives the magnetostaticfield information from the magnetic sensor, instead of a signal from thedemodulator, on a condition that the bypass circuit is enabled.
 11. TheTPMS sensor of claim 1, wherein the receiver is configured to receive anantenna signal generated from a second communication signal received byan external antenna coil, the TPMS sensor further comprising: amultiplexer configured to receive a first signal derived from themodulated low-frequency electromagnetic carrier signal or a secondsignal derived from the antenna signal, and selectively output one ofthe first signal or the second signal to the microcontroller unit. 12.The TPMS sensor of claim 1, wherein the receiver includes an antennacoil configured to receive a second communication signal and generate anantenna signal based on the second communication signal, the TPMS sensorfurther comprising: a multiplexer configured to receive a first signalderived from the modulated low-frequency electromagnetic carrier signalor a second signal derived from the antenna signal, and selectivelyoutput one of the first signal or the second signal to themicrocontroller unit.
 13. The TPMS sensor of claim 7, wherein thereceiver is configured to receive an antenna signal generated from asecond communication signal received by an external antenna coil, theTPMS sensor further comprising: a multiplexer configured to receive afirst signal derived one of the modulated low-frequency electromagneticcarrier signal and the magnetostatic field information or a secondsignal derived from the antenna signal, and selectively output one ofthe first signal or the second signal to the microcontroller unit. 14.The TPMS sensor of claim 13, further comprising a bypass circuitconfigured to be selectively enabled to bypass the demodulator such thatmultiplexer receives the magnetostatic field information from themagnetic sensor, instead of a signal from the demodulator, when thebypass circuit is enabled.
 15. The TPMS sensor of claim 1, furthercomprising a transmitter configure to transmit a radio frequency signalin response to the receiver receiving the at least one communicationsignal.
 16. The TPMS sensor of claim 1, wherein the modulatedlow-frequency electromagnetic carrier signal is modulated such that themodulated low-frequency electromagnetic carrier signal is present at acarrier frequent or not present according to an encoded time pattern,and the magnetic sensor is configured to detect the encoded time patternof the modulated low-frequency electromagnetic carrier signal andconvert the time pattern into the encoded measurement signal.
 17. Amethod for communicating with a tire pressure monitoring system (TPMS)sensor comprising a microcontroller unit and a receiver electricallyconnected to the microcontroller unit and configured to receive at leastone communication signal, wherein the receiver includes a magneticsensor, the method comprising: detecting, by the magnetic sensor, amodulated low-frequency electromagnetic carrier signal as a firstcommunication signal; outputting, by the magnetic sensor, an encodedmeasurement signal based on the detected modulated low-frequencyelectromagnetic carrier signal; converting, by a demodulator, theencoded measurement signal into a data signal; and outputting, by thedemodulator, the data signal to the microcontroller unit
 18. The methodof claim 17, further comprising: detecting, by the magnetic sensor,static magnetic fields; and transmitting, by the magnetic sensor,magnetostatic field information to the microcontroller unit.
 19. Themethod of claim 18, further comprising: selectively bypassing, by abypass circuit, the demodulator such that microcontroller unit receivesthe magnetostatic field information from the magnetic sensor, instead ofa signal from the demodulator, when the bypass circuit is enabled. 20.The method of claim 17, further comprising: receiving, by the receiver,an antenna signal generated from a second communication signal receivedby an external antenna coil; and selectively outputting, by amultiplexer, one of a first signal or a second signal to themicrocontroller unit, wherein the first signal is derived from themagnetic sensor and the second signal is derived from the antennasignal.